Prism - A ZX Spectrum Inspired Low Cost Acrylic Case

I’ve had a couple TGW71 PCBs for an absolute age (original board by @the_pokemon_kid)

It was my first SMD soldering project, I love the layout of a 60% plus arrows and nav cluster, and the RGB indicator light between them.

I’ve been planning an inexpensive case for them for a while but never got around to it.

I’m a fan of vintage mechanical keyboards (take a look at my post history!) and have a lot of beige, but thought that wouldn’t transfer over well to an acrylic sandwich case

Instead I thought I’d use the Sinclair ZX Spectrum family family for inspiration (particularly the the ones that came after the 48k),

I thought it was a good fit seeing as they have the same design philosophy in terms of keeping the costs low, and they use blocky aesthetics that could be emulated with an acrylic sandwich case.

My design uses vertical pieces of acrylic to slot into the case to have designs visible on multiple faces, and also to add some rigidity by keying into place.

I’m planning for the black layers of the case to be matte, though I haven’t settled on a material yet (not sure on the pros/cons of high impact polystyrene, ABS etc.) if anyone has any thoughts please let me know!

I rendered it with WoB keycaps because I have a spare set (so that’s probably what will end up on them) and it matches the WoB scheme used on all ZX Spectrums except the 48k. It would look great with KAM wraith keycaps too.

I originally planned on the plate being aluminium, but it came out as too expensive so I’m looking at PETG instead.

Since the first renders I made some changes to the plate design, and the pen rest (seeing as the design does not use 3mm black acrylic anywhere) I changed it so it can be either a solid piece (as before) or multiple to mirror the stripes of the top right of the board. This is how it’s looking at the moment:

This is also the first big(ish) thing I’ve designed in CAD (Fusion 360), so I’m looking for feedback, especially on how I can improve the rendering.

I’m currently looking at getting it made and waiting for some quotes to come back. Having quickly looked at ebay, the materials alone cost about £30.

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I’m digging it so far! Wonder how much it’d adjust the cost of production to bring in some of those carved horizontal lines on the top face from the original, since that’s a very cool design element imo.

Also might be worth experimenting with a couple different materials/production methods for the diffuser; acrylic diffusers leave a lot to be desired in terms of actual diffusion and you might be able to get some really neat, smooth effects out of other things like PLA.

Thanks! I did look at getting the black parts routed and made out of HDPE in which case I would definitely add the horizontal lines. Unfortunately I can’t find anyone that can do it, at least not on the cheap.

Can you get PLA in sheets? or is it only for 3D printing? Combining 3D printed and laser cut parts was not something I had considered before, but might be useful for future projects, you could have the versatility of the 3D print beneath, with the size and finish of the laser cut on top.

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I know enough to know that you can get PLA in sheets, but I’m not sure what thicknesses are easily-available. Combining 3D printing with other production methods was definitely rough for a while, but I think at the moment dealing with the tolerances is pretty viable with the right printers/settings.

This is really interesting! While the layout isn’t my cup of tea (f-rowless TKLs aren’t my fancy) I’d be all over an alternate version with a 60%-with-numpad layout!

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GMK Dots would look excellent on this. Love the vintage feel.

What price point are you targeting?

Honestly I’m probably just going to do this for myself, it would be a lot of work to turn it into a product. The PCB was a limited run of I think only 10 made in total and I’m not in contact with the original developer (it says /u/ca178858 on the board)

I’m happy to make the files for the case available once I’ve finished prototyping though. And if anyone is interested I can get in contact with the PCB designer to see if I can get hold of the gerbers.

If I remember correctly the PCB and components cost me about £30, the case I think will be between £20 and £40. If someone wanted to do a short run of ~100, I think pick and place would add £7 onto each PCB. So it could be made affordable and I’m sure there are cost reductions to be made by doing the case and PCB in bulk

I agree! Yet another great set of keycaps by Biip!

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Wowee this is awesome.

Will you consider offering the files in the future for people to make their own?

or alternatively have a GB?

I would be really interested if I could put a Spectrum PCB inside it. Would it fit?

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Most definitely, I’ll make the files available for the case once it’s all finished, though it wouldn’t really be useful without the PCB. If there is enough interest I’ll start pestering the original designer for the gerbers and BOM.

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No, not like this. You might be able to add more layers for to make space for it, but you’d probably end up with a very tall device (I am guessing thinness was one of the reasons for the “dead flesh” keyboard on the original 48k, as well as the cost cutting)

I really love the look & ideal of this case! I’ll be looking to get in on one if this goes to GB for sure! :+1:

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Made some minor changes to the case and did some more renders. Pretty pleased with some of them (Fusion 360 isn’t the easiest thing to get good render results in!)

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Looks good :+1:
Love the idea, definitely interested to buy one if/when available…

Interested, too. Also think, it should look perfect with KAM Wraith.

Nevertheless I’m mostly interested because I recently discovered that there are f-row-less TKL keyboards out there and I really like that idea. Namely I recently discovered the Cygnus TKL, so I probably won’t buy both.

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Update:

I made it! And it came to the UK meetup in Leeds a couple weeks ago.

It has been built with (basically what I had lying around) lubed Cherry Clears with switch films, 56g Novelkey springs, locking caps lock, very shiny OG WoB and GMK RGBYK.

I only ever really planned on making this for myself, but since there has been a fair of interest in actually getting this produced, I’ve started a github repo for it where you can find everything needed to make your own (although I would wait a little while).

This version was not quite right, it required a couple bits be cut by hand and for some of the inserts to be sanded down to fit. The changes have been carried over to the newest version, BUT they haven’t yet been tested.

Despite minor issues it’s a really solid board, clearance on components is PERFECT, satisfying heft, little flex in the case with the vertical layers adding rigidity, the PETG plate layers allow for a bit of plate flex and it has an overall muted thocky sound.

If you don’t want to go to the hassle of making your own PCB and case, there is a possibility (once I’ve ironed out some of the aforementioned issues) that Mechboards (who helped me with the prototype) may be convinced to do a run of it, if that happens there will probably be a proper interest check, but it couldn’t hurt to express interest here too!

More images:

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Looks nice!
makes me wanna make a black on white kit for KAM Wraith!

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Wow, this turned out so well!